Biomass Derived 3D Hierarchical Porous Activated Carbon for Solid-State Symmetric Supercapacitors

Abstract

This study reports on the valorization of Hyparrhenia hirta (biowaste) into a valuable electrode material for high-performance supercapacitor applications. Biowaste-derived activated carbons (ACs) with a tailorable porous texture are attained via a two-step process. Hence, a hydrothermally and microwave-irradiated (HSW) carbon shows a meso/microporous texture with a specific surface area of ~ 991 m2 g⁻1 and a pore size of 3.09 nm in diameter. The HSW electrode exhibits the highest specific capacitance (Cs) of ~ 501.6 F/g at 2 A/g in 1 M Na2SO4 aqueous electrolyte (three-electrode configuration), with an outstanding cyclability of 84.6% over 10,000 charge/discharge cycles at 10 A/g. A fabricated aqueous symmetric supercapacitor shows the highest specific capacitance of 106.6 F/g at 2 A/g in 1 M Na2SO4 aqueous solution, with the highest energy density of 33.3 W h/kg at a power density of 1500 W/kg. Further, a solid-state symmetric supercapacitor using a PVA/ Na2SO4 gel electrolyte exhibits Cs ~ 101.9 F/g at 2 A/g with a high energy density of ~ 31.8 W h/kg at a power density of ~ 1200 W/kg, as well as excellent cyclability up to 10,000 cycles. The auspicious outcomes strongly ensure a high possibility of eco-friendly electrode materials for supercapacitor applications.